This invention relates to the preparation of organosilicon compounds. In particular this invention relates to a method for the preparation of organosilicon compounds, and more particularly hydrocarbonhydrocarbonoxy silicon compounds, by the reaction of elemental silicon with hydrocarbon ethers.
The preparation of organoorganoxysilanes by the reaction of organometallic reagents with organoxysilanes has been known for over 100 years, but today's commercial silicone production is based on the more economical direct process reaction of organic halides, particularly methyl chloride, with various forms of metallic silicon at high temperature to produce organohalosilanes. From several points of view, such as minimum corrosion of processing equipment and by-product handling, organoorganoxysilanes are preferred over organohalosilanes as intermediates for the production of silicones. Consequently, a commercially attractive method for the production of organoorganoxysilanes is needed.
Rochow, U.S. Pat. No. 2,459,539 has reacted dialkyl ethers with silicon at elevated temperatures in the presence of a hydrogen halide to prepare alkyl-substituted halogenosilanes but not alkyl-substituted alkoxysilanes. This route to organosilicon compounds thus suffers many of the disadvantages of the aforesaid direct process route to organohalosilanes.
Bonitz, U.S. Pat. No. 3,505,379 discloses a process for preparing alkyl-substituted alkoxysilanes which avoids organochlorosilanes but which requires a hydrosilylation reaction. In addition to being a more expensive two-step process, the invention of Bonitz is not useful for preparing the commercially important methyl-substituted alkoxysilanes.
Yamada, et al., Japanese Pat. No. 187,342 have described the reaction of alkyl and aryl ethers with metallic silicon at atmospheric pressure in a flow-through, hot tube system to produce alkylalkoxysilanes and arylalkoxysilanes. Although very high temperatures were needed, it was theorized therein that alloying the metallic silicon with copper, silver, reduced copper or reduced silver could allow the reaction temperature to be reduced and the yield of product to be increased.
The method of Yamada, et al. has not been adopted as a method for the commercial production of silicone intermediates, in spite of its attractiveness. Although many reasons undoubtedly exist for this non-adoption, a main deterent to its adoption may be the work of Zuckerman, Ph.D. Thesis, Harvard University, 1960, which concluded that the reaction of ethers with silicon as stated by Yamada, et al. does not produce organosilicon compounds. Furthermore, Newton, et al. Inorg. Chem. 9, 1072 (1971) failed to produce methylmethoxysilanes from the reaction of dimethyl ether with a silicon-copper alloy in a silicone oil slurry.
In spite of these negative results, the desirability of preparing organosilicon compounds directly from silicon and hydrocarbon ethers spurred the following invention.